diff --git a/lua/eca/approve.lua b/lua/eca/approve.lua
new file mode 100644
index 0000000..5c5f5d8
--- /dev/null
+++ b/lua/eca/approve.lua
@@ -0,0 +1,101 @@
+local M = {}
+
+---@param tool_call eca.ToolCallRun
+function M.get_preview_lines(tool_call)
+  if not tool_call.details then
+    local arguments = vim.split(vim.inspect(tool_call.arguments), "\n")
+    local messages = {}
+    if tool_call.summary then
+      table.insert(messages, "Summary: " .. tool_call.summary)
+    end
+    table.insert(messages, "Tool Name: " .. tool_call.name)
+    table.insert(messages, "Tool Type: " .. tool_call.origin)
+    table.insert(messages, "Tool Arguments: ")
+    for _, v in pairs(arguments) do
+      table.insert(messages, v)
+    end
+    return messages
+  end
+  local lines = vim.split(tool_call.details.diff, "\n")
+  return { tool_call.details.path, unpack(lines) }
+end
+
+---@param lines string[]
+---@return {row: number, col: number, width: number, height: number}
+local function get_position(lines)
+  local gheight = math.floor(
+    vim.api.nvim_list_uis() and vim.api.nvim_list_uis()[1] and vim.api.nvim_list_uis()[1].height or vim.o.lines
+  )
+  local gwidth = math.floor(
+    vim.api.nvim_list_uis() and vim.api.nvim_list_uis()[1] and vim.api.nvim_list_uis()[1].width or vim.o.columns
+  )
+  local height = #lines > 10 and 35 or #lines
+  local width = 0
+  for _, line in ipairs(lines) do
+    if #line > width then
+      width = #line
+    end
+  end
+  return {
+    row = (gheight - height) * 0.5,
+    col = (gwidth - width) * 0.5,
+    width = math.floor(width * 1.5),
+    height = height,
+  }
+end
+
+---@param tool_call eca.ToolCallRun
+---@param on_accept function
+---@param on_deny function
+function M.display_preview_lines(tool_call, on_accept, on_deny)
+  local lines = M.get_preview_lines(tool_call)
+  local buf = vim.api.nvim_create_buf(false, false)
+  vim.api.nvim_buf_set_lines(buf, 0, -1, false, lines)
+  vim.api.nvim_set_option_value("modifiable", false, { buf = buf })
+  local position = get_position(lines)
+  local title = tool_call.summary or tool_call.name
+  local win = vim.api.nvim_open_win(buf, true, {
+    border = "single",
+    title = "Approve Tool Call(y/n): " .. title,
+    relative = "editor",
+    row = position.row,
+    col = position.col,
+    width = position.width,
+    height = position.height,
+  })
+  if tool_call.details then
+    vim.api.nvim_set_option_value("filetype", "diff", { buf = buf })
+  else
+    vim.api.nvim_set_option_value("number", false, { win = win })
+    vim.api.nvim_set_option_value("relativenumber", false, { win = win })
+  end
+
+  vim.keymap.set({ "n", "i" }, "y", "", {
+    buffer = buf,
+    callback = function()
+      vim.api.nvim_win_close(win, true)
+      vim.api.nvim_buf_delete(buf, { force = true })
+      if on_accept then
+        on_accept()
+      end
+    end,
+  })
+  vim.keymap.set({ "n", "i" }, "n", "", {
+    buffer = buf,
+    callback = function()
+      vim.api.nvim_win_close(win, true)
+      vim.api.nvim_buf_delete(buf, { force = true })
+      if on_deny then
+        on_deny()
+      end
+    end,
+  })
+end
+
+---@param tool_call eca.ToolCallRun
+---@param on_accept function
+---@param on_deny function
+function M.approve_tool_call(tool_call, on_accept, on_deny)
+  M.display_preview_lines(tool_call, on_accept, on_deny)
+end
+return M
diff --git a/lua/eca/mediator.lua b/lua/eca/mediator.lua
index 63c9ec0..a99ec96 100644
--- a/lua/eca/mediator.lua
+++ b/lua/eca/mediator.lua
@@ -12,11 +12,13 @@ end
 
 ---@param method string
 ---@param params eca.MessageParams
----@param callback fun(err: string, result: table)
+---@param callback? fun(err?: string, result?: table)
 function mediator:send(method, params, callback)
   if not self.server:is_running() then
-    callback("Server is not running, please start the server", nil)
-    return
+    if callback then
+      callback("Server is not running, please start the server", nil)
+    end
+    require("eca.logger").notify("Server is not rnning, please start the server", vim.log.levels.WARN)
   end
   self.server:send_request(method, params, callback)
 end
diff --git a/lua/eca/sidebar.lua b/lua/eca/sidebar.lua
index 8ddb940..d302425 100644
--- a/lua/eca/sidebar.lua
+++ b/lua/eca/sidebar.lua
@@ -880,7 +880,7 @@ function M:_set_welcome_content()
     "- **RepoMap**: Use `:EcaAddRepoMap` to add repository structure context",
     "",
     "---",
-    ""
+    "",
   }
 
   Logger.debug("Setting welcome content for new chat")
@@ -1204,6 +1204,7 @@ function M:handle_chat_content_received(params)
   end
 
   local content = params.content
+  local chat_id = params.chatId
 
   if content.type == "text" then
     -- Handle streaming text content
@@ -1234,6 +1235,8 @@ function M:handle_chat_content_received(params)
     self:_handle_tool_call_prepare(content)
     -- IMPORTANT: Return immediately - do NOT display anything for toolCallPrepare
     return
+  elseif content.type == "toolCallRun" then
+    self:render_tool_call(content, chat_id)
   elseif content.type == "toolCallRunning" then
     -- Show the accumulated tool call
     self:_display_tool_call(content)
@@ -1274,6 +1277,16 @@ function M:handle_chat_content_received(params)
   end
 end
 
+function M:render_tool_call(tool_content, chat_id)
+  if tool_content.type == "toolCallRun" and tool_content.manualApproval then
+    return require("eca.approve").approve_tool_call(tool_content, function()
+      self.mediator:send("chat/toolCallApprove", { chatId = chat_id, toolCallId = tool_content.id }, nil)
+    end, function()
+      self.mediator:send("chat/toolCallReject", { chatId = chat_id, toolCallId = tool_content.id }, nil)
+    end)
+  end
+end
+
 ---@param text string
 function M:_handle_streaming_text(text)
   -- Only check for empty text
diff --git a/lua/eca/types.lua b/lua/eca/types.lua
index 766de77..5ff312b 100644
--- a/lua/eca/types.lua
+++ b/lua/eca/types.lua
@@ -1,5 +1,14 @@
 ---@meta
 
+---@alias eca.ChatModel string
+---@alias eca.ChatBehavior 'agent'|'plan'
+---@class eca.ServerCapabilities
+---@field welcomeMessage string
+---@field models eca.ChatModel[]
+---@field defaultModel eca.ChatModel
+---@field behaviors eca.ChatBehavior[]
+---@field defaultBehavior eca.ChatBehavior
+
 ---@class eca.ChatContext
 ---@field type string
 ---@field path? string
@@ -9,7 +18,7 @@
 ---@field name? string
 ---@field description? string
 ---@field mimeType? string
----@field server string
+---@field server? string
 
 ---@class eca.ChatCommand
 ---@field name string
@@ -33,24 +42,30 @@
 ---@field linesAdded integer the count of lines added in this change
 ---@field linesRemoved integer the count of lines removed in this change
 
----@class eca.ToolCallRun
----@field type 'toolCallRun'
+---@class eca.ToolCallPrepare
+---@field type 'toolCallPrepare'
 ---@field origin eca.ToolCallOrigin
 ---@field id string the id of the tool call
 ---@field name string name of the tool
----@field arguments {[string]: string} arguments of the tool call
+---@field argumentsText {[string]: string} arguments of the tool call
 ---@field manualApproval boolean whether the call requires manual approval from the user
 ---@field summary string  summary text to present about this tool call
----@field details eca.ToolCallDetails extra details for the call. clients may use this to present a different UX for this tool call.
+--- extra details for the call. clients may use this to present a different UX
+--- for this tool call.
+---@field details eca.ToolCallDetails
+---
 
----@class eca.ToolCallRunning
----@field type 'toolCallRunning'
+---@class eca.ToolCallRun
+---@field type 'toolCallRun'
 ---@field origin eca.ToolCallOrigin
 ---@field id string the id of the tool call
 ---@field name string name of the tool
 ---@field arguments {[string]: string} arguments of the tool call
----@field summary? string  summary text to present about this tool call
----@field details? eca.ToolCallDetails extra details for the call. clients may use this to present a different UX for this tool call.
+---@field manualApproval boolean whether the call requires manual approval from the user
+---@field summary string  summary text to present about this tool call
+--- extra details for the call. clients may use this to present a different UX
+--- for this tool call.
+---@field details eca.ToolCallDetails
 
 ---@class eca.ToolCalled
 ---@field type 'toolCalled'
@@ -61,3 +76,11 @@
 ---@field outputs {type: 'text', text: string}[] the result of the tool call
 ---@field summary? string summary text to present about the tool call
 ---@field details? eca.ToolCallDetails extra details about the call
+
+---@class eca.UsageContent
+---@field type 'usage'
+---@field messageInputTokens number
+---@field messageOutputTokens number
+---@field sessionTokens number
+---@field messageCost? string
+---@field sessionCost? string
diff --git a/tests/stubs/tool_calls.lua b/tests/stubs/tool_calls.lua
new file mode 100644
index 0000000..097ad72
--- /dev/null
+++ b/tests/stubs/tool_calls.lua
@@ -0,0 +1,48 @@
+local stubs = {}
+
+stubs.read_file = {
+  arguments = {
+    path = "/Users/tgeorge/git/eca-nvim/hack/messages.lua",
+  },
+  id = "toolu_013zj73SHzZNoeE7kzD7qzb4",
+  manualApproval = true,
+  name = "eca_read_file",
+  origin = "native",
+  summary = "Reading file messages.lua",
+  type = "toolCallRun",
+}
+
+stubs.edit_file = {
+  arguments = {
+    new_content = 'local M = {}\n\n--- Show ECA messages using snacks.picker\nfunction M.show()\n  local has_snacks, picker = pcall(require, "snacks.picker")\n  if not has_snacks then\n    vim.notify("snacks.picker is not available", vim.log.levels.ERROR)\n    return\n  end\n\n  Snacks.picker(\n    ---@type snacks.picker.Config\n    {\n      source = "eca messages",\n      finder = function(opts, ctx)\n        ---@type snacks.picker.finder.Item[]\n        local items = {}\n        for msg in vim.iter(require("eca").server.messages) do\n          local decoded = vim.json.decode(msg.content)\n          table.insert(items, {\n            text = decoded.method,\n            idx = decoded.id,\n            preview = {\n              text = vim.inspect(decoded),\n              ft = "lua",\n},\n})\n        end\n        return items\n      end,\n      preview = "preview",\n      format = "text",\n      confirm = function(self, item, _)\n        vim.fn.setreg("", item.preview.text)\n        self:close()\n      end,\n }\n  )\nend\n\nreturn M',
+    original_content = 'local has_snacks, picker = pcall(require, "snacks.picker")\nif has_snacks then\n  Snacks.picker(\n    ---@type snacks.picker.Config\n    {\n      source = "eca messages",\n      finder = function(opts, ctx)\n        ---@type snacks.picker.finder.Item[]\n        local items = {}\n        for msg in vim.iter(require("eca").server.messages) do\n          local decoded = vim.json.decode(msg.content)\n          table.insert(items, {\n            text = decoded.method,\n            idx = decoded.id,\n            preview = {\n              text = vim.inspect(decoded),\n              ft = "lua",\n },\n })\n        end\n        return items\n      end,\n      preview = "preview",\n      format = "text",\n      confirm = function(self, item, _)\n        vim.fn.setreg("", item.preview.text)\n        self:close()\n      end,\n }\n  )\nend',
+    path = "/Users/tgeorge/git/eca-nvim/hack/messages.lua",
+  },
+  details = {
+    diff = '@@ -1, 5 +1, 13 @@\n-local has_snacks, picker = pcall(require, "snacks.picker")\n-if has_snacks then\n+local M = {}\n+\n+--- Show ECA messages using snacks.picker\n+function M.show()\n+  local has_snacks, picker = pcall(require, "snacks.picker")\n+  if not has_snacks then\n+    vim.notify("snacks.picker is not available", vim.log.levels.ERROR)\n+    return\n+  end\n+\n   Snacks.picker(\n     ---@type snacks.picker.Config\n     {\n@@ -29, 3 +37, 5 @@\n }\n   )\n end\n+\n+return M',
+    linesAdded = 12,
+    linesRemoved = 10,
+    path = "/Users/tgeorge/git/eca-nvim/hack/messages.lua",
+    type = "fileChange",
+  },
+  id = "toolu_01KAVb3qpJDcSnbnJmpUndQF",
+  manualApproval = true,
+  name = "eca_edit_file",
+  origin = "native",
+  summary = "Editting file",
+  type = "toolCallRun",
+}
+
+stubs.mcp = {
+  arguments = {
+    content = 'return "hello world"',
+    path = "/Users/tgeorge/git/eca-nvim/hack/test_mcp_write_file.lua",
+  },
+  id = "toolu_01B8xcb7csLRHvqrnAZTgzPi",
+  manualApproval = true,
+  name = "write_file",
+  origin = "mcp",
+  type = "toolCallRun",
+}
+
+return stubs
diff --git a/tests/test_approve.lua b/tests/test_approve.lua
new file mode 100644
index 0000000..17db288
--- /dev/null
+++ b/tests/test_approve.lua
@@ -0,0 +1,91 @@
+local MiniTest = require("mini.test")
+local eq = MiniTest.expect.equality
+local child = MiniTest.new_child_neovim()
+local stubs = require("tests.stubs.tool_calls")
+
+local T = MiniTest.new_set({
+  hooks = {
+    pre_case = function()
+      child.restart({ "-u", "scripts/minimal_init.lua" })
+      child.lua([[
+        _G.notifications = {}
+        _G.on_accept = function() table.insert(_G.notifications, "accept") end
+        _G.on_reject = function() table.insert(_G.notifications, "reject") end
+      ]])
+    end,
+    post_once = child.stop,
+  },
+})
+
+T["preview lines"] = function()
+  local test_cases = {
+    {
+      input = stubs.read_file,
+      want = {
+        "Summary: Reading file messages.lua",
+        "Tool Name: eca_read_file",
+        "Tool Type: native",
+        "Tool Arguments: ",
+        "{",
+        '  path = "/Users/tgeorge/git/eca-nvim/hack/messages.lua"',
+        "}",
+      },
+    },
+    {
+      input = stubs.edit_file,
+      want = {
+        "/Users/tgeorge/git/eca-nvim/hack/messages.lua",
+        "@@ -1, 5 +1, 13 @@",
+        '-local has_snacks, picker = pcall(require, "snacks.picker")',
+        "-if has_snacks then",
+        "+local M = {}",
+        "+",
+        "+--- Show ECA messages using snacks.picker",
+        "+function M.show()",
+        '+  local has_snacks, picker = pcall(require, "snacks.picker")',
+        "+  if not has_snacks then",
+        '+    vim.notify("snacks.picker is not available", vim.log.levels.ERROR)',
+        "+    return",
+        "+  end",
+        "+",
+        "   Snacks.picker(",
+        "     ---@type snacks.picker.Config",
+        "     {",
+        "@@ -29, 3 +37, 5 @@",
+        " }",
+        "   )",
+        " end",
+        "+",
+        "+return M",
+      },
+    },
+    {
+      input = stubs.mcp,
+      want = {
+        "Tool Name: write_file",
+        "Tool Type: mcp",
+        "Tool Arguments: ",
+        "{",
+        "  content = 'return \"hello world\"',",
+        '  path = "/Users/tgeorge/git/eca-nvim/hack/test_mcp_write_file.lua"',
+        "}",
+      },
+    },
+  }
+  for _, test_case in pairs(test_cases) do
+    local got = child.lua_get('require("eca.approve").get_preview_lines(...)', { test_case.input })
+    eq(got, test_case.want)
+  end
+end
+
+T["tool approval calls callback"] = function()
+  child.lua("_G.tool_call = " .. vim.inspect(stubs.read_file))
+  child.lua('require("eca.approve").approve_tool_call(_G.tool_call, _G.on_accept, _G.on_reject)')
+  child.type_keys("y")
+  eq(child.lua_get("_G.notifications"), { "accept" })
+  child.lua('require("eca.approve").approve_tool_call(_G.tool_call, _G.on_accept, _G.on_reject)')
+  child.type_keys("n")
+  eq(child.lua_get("_G.notifications"), { "accept", "reject" })
+end
+
+return T